1. Field of the Invention.
This invention relates to a method and apparatus for assembling washer members with fastener members.
2. Description of the Invention.
In the past, various fasteners and washers have been mechanically assembled. The types of fastener/washer assemblies may be generally categorized in two areas, sliding fit assemblies and interference fit assemblies.
In the sliding type fit assemblies, a fastener and washer having a sliding fit therebetween are assembled together. In some cases, subsequent operations are performed on the shank of the fastener of the assemblies such as, for example, thread rolling, forming a ring on the shank, or using the assembly in subsequent assembly operations. Since rolled threads on the shank may be larger in diameter than the opening in the washer, the washer is retained on the shank after the threads are formed. When a ring is formed on the shank of the fastener the washer is retained on the shank of the fastener. In other cases, the assembly may be fed to subsequent automatic assembly operations for securing different parts together with the washer/fastener assembly.
In the interference type fit washer/fastener assembly there is an interference fit between the washer and the shank of the fastener requiring some force, dependent on the amount of the interference fit, to assemble fasteners and washers. Other subsequent operations may be performed on interference fit type assemblies such as described above in connection with the sliding fit type assemblies.
In the assembly of washers and fasteners, it is highly desirable to assemble the parts at a high rate of speed to maintain the production rates of associated equipment. Substantial advances have been made in the rates at which the manufacturing equipment can form fasteners and washers. The equipment used to perform subsequent operations on the fastener and washer assemblies have also been developed to reach higher speeds. For example, rotary thread rolling equipment is now available with a capability of forming threads on a fastener up to 800 parts per minute and equipment for forming a ring on the shank of the fastener has operated at the rate of 6,000 parts per minute. It is highly desirable to assemble washers and fasteners at a rate that is compatible with the associated equipment so that assembly of the washers and fasteners does not act as a bottleneck in the production process.
Known methods and apparatuses for assembling a washer and a fastener have required the use of intermittent motion devices which impede the rate at which the washers and fasteners may be assembled. One such known method and apparatus is disclosed in Pomernacki, U.S. Pat. Nos. 3,750,206 and 3,896,539. Such a method and apparatus has provided leaf springs to urge the fasteners and washers into an assembled relationship at the particular point of contact of the spring and fastener. These springs do not provide a smooth, even, continually sliding movement of the fastener into assembled relationship with the washer but rather require an abrupt or "intermittent" movement of the fastener at a particular point. Such intermittent type motion impedes the rate at which such a method and apparatus may be operated. In addition, the leaf spring "floats" at higher speeds since there is not sufficient time for the spring finger to move. Furthermore, the leaf springs do not provide any positive assembly positioning of the washers and fasteners and may flex and move in various directions which creates misalignment of the washer during the assembly process. Another problem of using leaf springs to assemble washers and fasteners arises in the assembly of washers and fasteners of the interference fit type. Such substantial forces are necessary to assemble these parts, that when such an apparatus is operated at a high rate of speed, the leaf springs are rendered ineffective. Such a method and apparatus also provides a reciprocating spring-loaded finger to position the fasteners as they are fed. Such an "intermittent" motion device limits the speed of such a method and apparatus.
Another known apparatus provides reciprocating spring-loaded feeder bars for feeding fasteners and washers into cleats on a straight line commercially available conveyor chain. Each of the cleats has a cavity therein for receiving a washer and a fastener. A linear surface is provided along a linear portion of the cleats to move the washers and fasteners together. Such an "intermittent" type feeder design limits the speed of such an apparatus. Certain problems incurred at higher speeds of such an apparatus include the timing of the cleats with the feeder bars, "floating" of the feeder bar, the relatively horizontal position of the fasteners and relatively vertical position of the fasteners as they are fed into the cleats and the washers and fasteners are free to move in the cleats.
Another problem of such an apparatus when operated at higher speeds is a change in dimension between the cleats since the chain on which the cleats are mounted may change in dimension. If the chain is in tension, such as when it is pulled, the chain may stretch and the cleats move out of alignment. If, on the other hand the chain is in compression, such as when it is pushed, it may buckle and the cleats move out of alignment. In addition, contaminants may build up between the cleats to move the cleats out of alignment. Another problem of such an apparatus at higher speeds is that continuous feeding of the part cannot be provided since there is no continuous surface upon which to feed. In addition, the design of such a machine is severely restricted in that commercially available chain is used. Generally, commercially available chain is not available in a size which corresponds to the size of various fasteners which are desired to be assembled by such a machine and undesired spacing between the fasteners is necessary. Another problem of such a machine when operated at higher speeds is the control of the conveyor chain and consequently the cleats thereon. Such a machine does not provide for controlling the movement of the chain and cleats in the lateral direction that is the direction at 90.degree. to the direction of motion of the conveyor.
The present invention relates to a method and apparatus for assembling washer members with fastener members at a high rate of speed. Such a high rate of speed is provided by assembling the washers and fasteners together with an even, smooth, continuous motion to allow such high production rates to be achieved.
Methods and apparatuses of the present invention provide for moving a plurality of one of the fasteners and the washers along a helical path and the other of the fasteners and the washers in a circular path and simultaneously therewith increasing the telescopic assembled relationship between the fasteners and the washers. An apparatus described herein whereby said methods may be practiced includes a base and an assembly wheel having a plurality of pockets about the periphery thereof. The assembly wheel is rotatably mounted on the base and means are provided for continuously rotating the wheel at predetermined speeds. Means are provided for feeding the washers in an oriented position into the pockets in the wheel. The pockets have a hook portion downstream of the direction of rotation of the wheel for retaining one of the washers in an oriented position in the pocket of the wheel. Means are provided for feeding the fasteners in an oriented position into the pockets of the wheel. The hook portion receives a fastener from the feeding means and retains the fastener in an oriented position in the pocket and also provides for alignment between the washer and fastener as they are assembled. A stationary arcuate cam is secured to the base and extends about a periphery of the wheel after the fasteners and washers are received in the pockets in the wheel. The arcuate cam has an arcuate cam surface for effecting simultaneous relative movement of a plurality of the fasteners and washers, by moving a plurality of one of the fasteners and washers along a helical path and simultaneously therewith increasing the telescopic assembled relationship between the shank portions of a plurality of the fasteners and the washers.
The apparatus of the present invention is capable of assembling washers and fasteners of both the sliding fit type and the interference fit type. During assembly of the washers and fasteners, the present invention provides for the positive control of each of the parts as they are assembled and is capable of exerting substantial forces to move the washers and fasteners, particularly of the interference fit type, together. The present invention also provides for a washer/fastener assembling apparatus having less moving parts which minimizes the cost of manufacture of such an apparatus, the timing problems realized when a number of moving parts are required, and also the problems that may be incurred during the use of the machine in production. The apparatus of the present invention does not require any "intermittent" type moving parts during the assembly of the washers and fasteners.